It is known to load particulate matter from one container to another pneumatically, i.e., through the use of a stream of air. Such systems are commonly used, for example, to load particulate matter into the pneumatic tank of a truck trailer from another vessel, such as a railroad car. The types of materials that can be loaded in this way include flour, grain, fertilizer, plastic pellets, and so on.
Typically, the pneumatic trailers that are used in these systems have a positive displacement pump attached thereto. The vacuum side of this pump is fluidly attached to the interior of the trailer tank, while the trailer tank is itself fluidly connected to the rail car.
In use, the pump partially evacuates the trailer tank. The lower-than-atmospheric pressure in the trailer tank in turn draws a stream of air and particulate matter into the tank from the rail car. Systems of this type typically employ vacuum pumps that operate in the range of 400-800 cubic feet per minute. The systems are typically able to fill a trailer tank of 1600 cubic feet in 1 hour.
It is in the nature of these systems that the air withdrawn from the truck tank by the positive displacement pump during loading has a large amount of particulate matter suspended therein. This suspended particulate matter must be removed during the loading operation, because not doing so would cause unacceptable damage to the displacement pump as well result in an unacceptable loss of the product being unloaded from the rail car.
Prior commercial pneumatic loading systems having generally used cyclones, filters, or a combination of these devices to perform this separating function. The separating devices are generally disposed in the fluid pathway between the trailer tank and the displacement pump. They generally have had complicated flow patterns, and have used bulky components.
These basic flaws have resulted in a number of corollary problems. For example, the separating devices of the prior commercial systems generally have been expensive to produce. Moreover, their size has dictated that they be outside the trailer tank, generally at the back of the trailer. This, in turn, places the separating devices at a long distance from the displacement pump, which is typically located at the front of the trailer, thus requiring more tubing and resulting in a greater head loss of the supply vacuum.
As an additional difficultly, these prior separating systems have been difficult to clean. Since the separating systems must be cleaned between loads of different materials, this difficulty has posed logistical problems. For example, appropriate facilities to clean the separating system would have to exist at each loading site, if dissimilar loads are carried on each leg of a two-way journey.
It is therefore an object of the present invention to solve these and other associated difficulties that have heretofore existed with known pneumatic loading devices.
In order to achieve this and other objectives, the present invention provides a filter unit within the interior of the tank of the truck trailer. Preferably, the filter unit, along with its associated mounting and protective hardware, is disposed entirely within the circumference of one of the standard manholes of the tank.
While in its broader aspect the invention can use any filter media, the invention also includes providing an improved arrangement of mounting standard, commercially available filtering media within the unit. Consequently, the unit is more compact than the typical separating filters that have been used in this type of application previously.
When the filter unit is arranged in this way, the accumulated particulate matter that is separated by the filtering media falls directly back into the truck tank under the action of gravity, without the need of conduits or other devices to convey the collected matter from the separating system to the tank. This results in the present system being simpler than prior systems, with lower material costs. Because the separating system is disposed almost entirely within the tank, it places no additional demands on the overall size of the truck trailer. Moreover, the separating system can be placed near the front of the tank, closer to the vacuum pump, than can the typical prior-art system, reducing the length of the fluid conduit and thereby further increasing the efficiency of the device and further reducing the material costs. Still further, the compactness of the system allows the typical installation to include mechanisms to store spare, clean filter units in additional manholes, making on-site cleaning and changing of the filter system more practical.
With these and other aspects of the present invention in mind, there will now be described a particular embodiment. It should of course be borne in mind that this description is one of example only, and that the described embodiment should not be taken as unjustly limiting the scope the appended claims.